target/linux/brcm2708/patches-3.18/0112-Fix-grabbing-lock-from-atomic-context-in-i2c-driver.patch

   1 From 58ee33ad32d4a00735252718f8bac3f7592af6e7 Mon Sep 17 00:00:00 2001
   2 From: jeanleflambeur <catalin.vasile@gmail.com>
   3 Date: Sun, 1 Feb 2015 12:35:38 +0100
   4 Subject: [PATCH 112/114] Fix grabbing lock from atomic context in i2c driver
   5
   6 2 main changes:
   7 - check for timeouts in the bcm2708_bsc_setup function as indicated by this comment:
   8       /* poll for transfer start bit (should only take 1-20 polls) */
   9   This implies that the setup function can now fail so account for this everywhere it's called
  10 - Removed the clk_get_rate call from inside the setup function as it locks a mutex and that's not ok since we call it from under a spin lock.
  11
  12 removed dead code and update comment
  13
  14 fixed typo in comment
  15 ---
  16  drivers/i2c/busses/i2c-bcm2708.c | 90 +++++++++++++++++++++++++++++-----------
  17  1 file changed, 65 insertions(+), 25 deletions(-)
  18
  19 --- a/drivers/i2c/busses/i2c-bcm2708.c
  20 +++ b/drivers/i2c/busses/i2c-bcm2708.c
  21 @@ -68,6 +68,7 @@
  22  #define BSC_S_TA               0x00000001
  23
  24  #define I2C_TIMEOUT_MS 150
  25 +#define I2C_WAIT_LOOP_COUNT 40
  26
  27  #define DRV_NAME       "bcm2708_i2c"
  28
  29 @@ -86,6 +87,7 @@ struct bcm2708_i2c {
  30         void __iomem *base;
  31         int irq;
  32         struct clk *clk;
  33 +       u32 cdiv;
  34
  35         struct completion done;
  36
  37 @@ -109,10 +111,10 @@ static void bcm2708_i2c_init_pinmode(int
  38         int pin;
  39         u32 *gpio = ioremap(GPIO_BASE, SZ_16K);
  40
  41 -        BUG_ON(id != 0 && id != 1);
  42 +       BUG_ON(id != 0 && id != 1);
  43         /* BSC0 is on GPIO 0 & 1, BSC1 is on GPIO 2 & 3 */
  44         for (pin = id*2+0; pin <= id*2+1; pin++) {
  45 -printk("bcm2708_i2c_init_pinmode(%d,%d)\n", id, pin);
  46 +               printk("bcm2708_i2c_init_pinmode(%d,%d)\n", id, pin);
  47                 INP_GPIO(pin);          /* set mode to GPIO input first */
  48                 SET_GPIO_ALT(pin, 0);   /* set mode to ALT 0 */
  49         }
  50 @@ -151,16 +153,16 @@ static inline void bcm2708_bsc_fifo_fill
  51                 bcm2708_wr(bi, BSC_FIFO, bi->msg->buf[bi->pos++]);
  52  }
  53
  54 -static inline void bcm2708_bsc_setup(struct bcm2708_i2c *bi)
  55 +static inline int bcm2708_bsc_setup(struct bcm2708_i2c *bi)
  56  {
  57 -       unsigned long bus_hz;
  58         u32 cdiv, s;
  59         u32 c = BSC_C_I2CEN | BSC_C_INTD | BSC_C_ST | BSC_C_CLEAR_1;
  60 +       int wait_loops = I2C_WAIT_LOOP_COUNT;
  61
  62 -       bus_hz = clk_get_rate(bi->clk);
  63 -       cdiv = bus_hz / baudrate;
  64 -       if (cdiv > 0xffff)
  65 -               cdiv = 0xffff;
  66 +       /* Can't call clk_get_rate as it locks a mutex and here we are spinlocked.
  67 +        * Use the value that we cached in the probe.
  68 +        */
  69 +       cdiv = bi->cdiv;
  70
  71         if (bi->msg->flags & I2C_M_RD)
  72                 c |= BSC_C_INTR | BSC_C_READ;
  73 @@ -177,17 +179,25 @@ static inline void bcm2708_bsc_setup(str
  74                    - Both messages to same slave address
  75                    - Write message can fit inside FIFO (16 bytes or less) */
  76                 if ( (bi->nmsgs > 1) &&
  77 -                   !(bi->msg[0].flags & I2C_M_RD) && (bi->msg[1].flags & I2C_M_RD) &&
  78 -                    (bi->msg[0].addr == bi->msg[1].addr) && (bi->msg[0].len <= 16)) {
  79 +                       !(bi->msg[0].flags & I2C_M_RD) && (bi->msg[1].flags & I2C_M_RD) &&
  80 +                        (bi->msg[0].addr == bi->msg[1].addr) && (bi->msg[0].len <= 16)) {
  81                         /* Fill FIFO with entire write message (16 byte FIFO) */
  82 -                       while (bi->pos < bi->msg->len)
  83 +                       while (bi->pos < bi->msg->len) {
  84                                 bcm2708_wr(bi, BSC_FIFO, bi->msg->buf[bi->pos++]);
  85 +                       }
  86                         /* Start write transfer (no interrupts, don't clear FIFO) */
  87                         bcm2708_wr(bi, BSC_C, BSC_C_I2CEN | BSC_C_ST);
  88 +
  89                         /* poll for transfer start bit (should only take 1-20 polls) */
  90                         do {
  91                                 s = bcm2708_rd(bi, BSC_S);
  92 -                       } while (!(s & (BSC_S_TA | BSC_S_ERR | BSC_S_CLKT | BSC_S_DONE)));
  93 +                       } while (!(s & (BSC_S_TA | BSC_S_ERR | BSC_S_CLKT | BSC_S_DONE)) && --wait_loops >= 0);
  94 +
  95 +                       /* did we time out or some error occured? */
  96 +                       if (wait_loops < 0 || (s & (BSC_S_ERR | BSC_S_CLKT))) {
  97 +                               return -1;
  98 +                       }
  99 +
 100                         /* Send next read message before the write transfer finishes. */
 101                         bi->nmsgs--;
 102                         bi->msg++;
 103 @@ -197,6 +207,8 @@ static inline void bcm2708_bsc_setup(str
 104                 }
 105         }
 106         bcm2708_wr(bi, BSC_C, c);
 107 +
 108 +       return 0;
 109  }
 110
 111  static irqreturn_t bcm2708_i2c_interrupt(int irq, void *dev_id)
 112 @@ -204,13 +216,15 @@ static irqreturn_t bcm2708_i2c_interrupt
 113         struct bcm2708_i2c *bi = dev_id;
 114         bool handled = true;
 115         u32 s;
 116 +       int ret;
 117
 118         spin_lock(&bi->lock);
 119
 120         /* we may see camera interrupts on the "other" I2C channel
 121 -           Just return if we've not sent anything */
 122 -        if (!bi->nmsgs || !bi->msg )
 123 +                  Just return if we've not sent anything */
 124 +       if (!bi->nmsgs || !bi->msg) {
 125                 goto early_exit;
 126 +       }
 127
 128         s = bcm2708_rd(bi, BSC_S);
 129
 130 @@ -218,13 +232,16 @@ static irqreturn_t bcm2708_i2c_interrupt
 131                 bcm2708_bsc_reset(bi);
 132                 bi->error = true;
 133
 134 +               bi->msg = 0; /* to inform the that all work is done */
 135 +               bi->nmsgs = 0;
 136                 /* wake up our bh */
 137                 complete(&bi->done);
 138         } else if (s & BSC_S_DONE) {
 139                 bi->nmsgs--;
 140
 141 -               if (bi->msg->flags & I2C_M_RD)
 142 +               if (bi->msg->flags & I2C_M_RD) {
 143                         bcm2708_bsc_fifo_drain(bi);
 144 +               }
 145
 146                 bcm2708_bsc_reset(bi);
 147
 148 @@ -232,8 +249,19 @@ static irqreturn_t bcm2708_i2c_interrupt
 149                         /* advance to next message */
 150                         bi->msg++;
 151                         bi->pos = 0;
 152 -                       bcm2708_bsc_setup(bi);
 153 +                       ret = bcm2708_bsc_setup(bi);
 154 +                       if (ret < 0) {
 155 +                               bcm2708_bsc_reset(bi);
 156 +                               bi->error = true;
 157 +                               bi->msg = 0; /* to inform the that all work is done */
 158 +                               bi->nmsgs = 0;
 159 +                               /* wake up our bh */
 160 +                               complete(&bi->done);
 161 +                               goto early_exit;
 162 +                       }
 163                 } else {
 164 +                       bi->msg = 0; /* to inform the that all work is done */
 165 +                       bi->nmsgs = 0;
 166                         /* wake up our bh */
 167                         complete(&bi->done);
 168                 }
 169 @@ -266,22 +294,33 @@ static int bcm2708_i2c_master_xfer(struc
 170         bi->nmsgs = num;
 171         bi->error = false;
 172
 173 -       bcm2708_bsc_setup(bi);
 174 +       ret = bcm2708_bsc_setup(bi);
 175
 176 -       /* unlockig _after_ the setup to avoid races with the interrupt routine */
 177         spin_unlock_irqrestore(&bi->lock, flags);
 178
 179 -       ret = wait_for_completion_timeout(&bi->done,
 180 -                       msecs_to_jiffies(I2C_TIMEOUT_MS));
 181 +       /* check the result of the setup */
 182 +       if (ret < 0)
 183 +       {
 184 +               dev_err(&adap->dev, "transfer setup timed out\n");
 185 +               goto error_timeout;
 186 +       }
 187 +
 188 +       ret = wait_for_completion_timeout(&bi->done, msecs_to_jiffies(I2C_TIMEOUT_MS));
 189         if (ret == 0) {
 190                 dev_err(&adap->dev, "transfer timed out\n");
 191 -               spin_lock_irqsave(&bi->lock, flags);
 192 -               bcm2708_bsc_reset(bi);
 193 -               spin_unlock_irqrestore(&bi->lock, flags);
 194 -               return -ETIMEDOUT;
 195 +               goto error_timeout;
 196         }
 197
 198 -       return bi->error ? -EIO : num;
 199 +       ret = bi->error ? -EIO : num;
 200 +       return ret;
 201 +
 202 +error_timeout:
 203 +       spin_lock_irqsave(&bi->lock, flags);
 204 +       bcm2708_bsc_reset(bi);
 205 +       bi->msg = 0; /* to inform the interrupt handler that there's nothing else to be done */
 206 +       bi->nmsgs = 0;
 207 +       spin_unlock_irqrestore(&bi->lock, flags);
 208 +       return -ETIMEDOUT;
 209  }
 210
 211  static u32 bcm2708_i2c_functionality(struct i2c_adapter *adap)
 212 @@ -406,6 +445,7 @@ static int bcm2708_i2c_probe(struct plat
 213                 cdiv = 0xffff;
 214                 baudrate = bus_hz / cdiv;
 215         }
 216 +       bi->cdiv = cdiv;
 217
 218         dev_info(&pdev->dev, "BSC%d Controller at 0x%08lx (irq %d) (baudrate %d)\n",
 219                 pdev->id, (unsigned long)regs->start, irq, baudrate);